Recent advancement in inertial sensor technology has enabled high performing and low cost accelerometer and gyroscope sensors. An accelerometer sensor measures proper linear acceleration while a gyroscope sensor measures angular rotation or rotation rate. The linear acceleration and rotation measurements complement each other, and when they are combined, it is possible to recover the full sensor motion for tracking and navigation purposes.
When worn by a human body, accelerometers and gyroscopes enable direct and non-intrusive body motion data collection that can be used for gait and activity analysis. With the growing popularity and strong demands in smart mobile devices such as smart phones, smart watches, etc., there is a huge potential in motion analysis using the embedded accelerometer and gyroscope sensors for gait biometrics and activity recognition applications.
Motion analysis using accelerometers for gait biometrics and activity recognition has been an active research area for the past decade. More recently, the use of gyroscopes has also been explored in addition to accelerometers as well. However, despite the surge in research efforts, the practical application of these sensors for gait analysis remains a challenge due to data dependency on sensor placement: the accelerations or rotations are measured along the sensor axis. These measurements change with sensor orientation even when body motion stays the same. Most existing research is conducted in fixed laboratory settings with restricted sensor placement to bypass this problem, and is vulnerable in real world usage where the placement of mobile devices is casual and even arbitrary. Although promising performance has been reported in well-controlled studies using accelerometers and gyroscopes, there is still a large gap between existing research and real world applications.
What is needed is an improved way to handle variation in sensor orientation and address variations in sensor placement for the purpose of gait biometric and activity recognition.